CN110542525B - Method for testing vibration fatigue performance of metal in axial resonance state - Google Patents
Method for testing vibration fatigue performance of metal in axial resonance state Download PDFInfo
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Abstract
The invention provides a method for testing vibration fatigue performance of metal in an axial resonance state, which comprises the following steps: selecting a test piece, attaching a strain gauge, and measuring the response acceleration-strain/stress relation of the test piece in a resonance state; calculating the response acceleration of the test piece during formal test by combining the planned stress level; carrying out modal testing on the test piece to obtain an inherent frequency point and a response amplitude ratio of axial vibration; setting excitation frequency according to the natural frequency point, and calculating excitation acceleration according to the response amplitude ratio measured by the test; fine-tuning the real-time excitation acceleration value during the test to enable the target response acceleration to change within +/-2%; setting a resonance search and a resonance residence program to enable the test piece to keep a resonance state in the test process, and stopping the test when the response acceleration of the test piece suddenly drops or the test piece is broken; and acquiring the cycle number of the vibration system when the test is stopped. The invention adopts a vibration mode to carry out axial fatigue test on the metal material, and can greatly shorten the test period.
Description
Technical Field
The invention belongs to the technical field of resonance fatigue, and particularly relates to a vibration fatigue performance testing method under a metal axial resonance state.
Background
During ground operation and in air flight, certain parts on the aircraft are always in aerodynamic load and noise environment, and random vibration stress is generated at the parts due to excitation of the noise and aerodynamic load. Some structures, such as the rudder surface, horizontal tail, vertical tail, ventral fin, and pylon, also generate vibrational stress due to turbulence. The fatigue phenomenon caused by such a vibration stress is vibration fatigue.
The problems involved in solving the dynamic fatigue of a structure are many, and dynamic fatigue analysis is one of the important problems. For dynamic fatigue analysis of a structure, a dynamic fatigue SN curve is required. In general, the dynamic fatigue SN curve must be determined by dynamic fatigue testing. The dynamic fatigue test can be carried out on a vibration table.
The degree of response is much more severe when the structure is at resonance than when it is not, and fatigue failure of the structure tends to occur at resonance.
The working frequency of the hydraulic servo fatigue testing machine widely used at present is about dozens to one hundred hertz. Most parts can bear loads with higher frequency in work, and a common fatigue testing machine cannot achieve such high-frequency output, so that a test result possibly has certain difference with the actual working life, an original fatigue performance testing method needs to be changed, and the load frequency is improved, so that the fatigue performance measured by materials can be directly used in the actual working condition.
In addition, assuming that the test frequency is 50Hz, 10 is to be completed7A secondary cycle, wherein the total test time is approximately two and a half days; if the ultra-high cycle fatigue test is performed, a longer time is required, and thus the time cost required for the ordinary fatigue test is high.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides the vibration fatigue performance testing method under the metal axial resonance state, so that the sample piece is possible to be in the resonance state in the axial direction, and the fatigue performance of the sample piece is further measured in the axial direction.
The technical scheme for solving the technical problems is as follows: a vibration fatigue performance test method under a metal axial resonance state comprises the following steps:
(1) selecting a test piece, attaching a strain gauge, and measuring the response acceleration-strain/stress relation of the test piece in a resonance state;
(2) calculating the response acceleration of the test piece during formal test according to the response acceleration-strain/stress relation and by combining the planned stress level;
(3) carrying out modal testing on the test piece to obtain a natural frequency point and a response amplitude ratio of axial vibration of the test piece;
(4) setting excitation frequency according to the natural frequency point measured by the test piece, and calculating excitation acceleration according to the response amplitude ratio measured by the test piece;
(5) during testing, the real-time excitation acceleration value of the test piece is combined for fine adjustment, so that the target response acceleration change of the test piece in the testing process is within +/-2%;
(6) setting a resonance search and a resonance residence program to enable the test piece to keep a resonance state in the test process, and stopping the test when the response acceleration of the test piece suddenly drops or the test piece is broken; and acquiring the cycle number of the vibration system when the test is stopped.
The invention is further configured that in the step (1), the method for selecting the test piece comprises the following steps: and acquiring the buckling value and the modal parameter of the test piece to determine whether the test piece can be used for the axial resonance state vibration fatigue performance test.
The invention further provides that in the step (3), the method for acquiring the natural frequency point and the response amplitude ratio of the axial vibration of the sample comprises the following steps:
firstly, carrying out resonance exploration on the test piece to obtain a resonance frequency point of the test piece and a response acceleration value of the point;
secondly, calculating an extreme value of the difference value of the response accelerations of the acceleration sensor on the mass block for the ith time (i is more than or equal to 1 and less than or equal to n), wherein the ratio of the extreme value of the difference value to the average value of the multiple response accelerations is xiSquaring the mean ratio of the single calculation to obtain xi 2Then the square value of the ratio of the average value of n times (n is more than or equal to 3) of resonance exploration is summed and the root is extracted, namely
If the obtained value is within 1 percent, namely Y is less than or equal to 1 percent, the response coaxiality of the test piece is good, otherwise, the response coaxiality of the test piece is not good.
The invention is further set that the method for resonance exploration of the test piece is sine sweep frequency exploration, pre-exploration is carried out firstly, and then formal exploration is carried out, and the control elements comprise: controlling acceleration, frequency sweep range, frequency sweep rate and frequency sweep cycle number; the control acceleration of the pre-probing is 0.1-2g, the sweep frequency range is 5-2000Hz, the sweep frequency rate is 0.5-2Oct/min, one sweep frequency cycle comprises a forward one time and a reverse one time, and the resonance frequency point of the forward sweep frequency and the reverse sweep frequency and the response acceleration value of the point are obtained; and adjusting and controlling the acceleration, the frequency range and the frequency sweeping rate according to the control parameters of the formal exploration according to the pre-exploration result.
The invention is further set that the method for resonance exploration of the test piece is a random exploration method, pre-exploration is carried out firstly, then formal exploration is carried out, and the control elements comprise: controlling power spectral density value, frequency range, vibration duration; control power spectral density value of 0.001-0.05g for pre-probing2A white noise spectrum with the frequency range of 5-2000Hz and the vibration duration of the test piece after the response is stable is 30-120 seconds, and a resonance frequency point and a corresponding response acceleration value of the test piece are obtained; and adjusting the control power spectral density value and the frequency range according to the pre-probing result by the control parameters of the formal probing, and controlling the vibration duration of the test piece after the response is stable.
The invention is further set up in step (1), on the natural frequency point of the test piece, input not less than 3 different excitation accelerations, its different response levels include the fatigue performance of the material in high and low cycles, each excitation acceleration gathers the strain data of many cycles after the test piece is stabilized, then fit the response acceleration-strain relation;
according to the response acceleration-strain relation, calculating the response acceleration-stress relation according to the formula (I):
sigma ═ E epsilon (one)
In the formula: σ is the stress, E is the elastic modulus of the material, and ε is the measured strain of the test piece.
The invention is further set to collect strain data of 1000-10000 times of cycle period after each excitation acceleration is stable.
The method is further set to obtain the response acceleration value of the test piece during the test according to the response acceleration-stress relation and the planned stress level, then execute the first step and the second step to obtain the axial natural frequency point and the response amplitude ratio of the test piece, and obtain the excitation acceleration and the frequency value during the formal test.
The invention is further arranged to set a resonance search and resonance dwell program according to the measured values of the excitation acceleration and frequency of the test piece:
a. the natural frequency point of the test piece is +/-10 Hz;
b. calculating the excitation acceleration according to the corresponding stress level and amplitude ratio, and constantly controlling the excitation acceleration value;
c. a-90 phase tracking is used.
The invention is further configured to fit an SN curve or a gN curve after obtaining the number of cycles of the vibration system when the test is stopped.
The invention has the following beneficial effects: the invention adopts a vibration mode to carry out axial fatigue test on the metal material, and can greatly shorten the test period.
Drawings
FIG. 1 is a lift diagram;
FIG. 2 is a schematic of fatigue S-N curve fitting;
FIG. 3 is a graph of strain versus response acceleration;
FIG. 4 is a 7050 axial resonance fatigue SN curve;
FIG. 5 is a flowchart of a method for testing the vibration fatigue performance of a metal in an axial resonance state according to an embodiment of the present invention;
FIG. 6 is a schematic view of an axial resonance fatigue testing system in use with an embodiment of the present invention;
FIG. 7 is a schematic structural diagram of an axial resonance fatigue testing apparatus in an application of an embodiment of the present invention;
FIG. 8 is a cross-sectional view of the axial resonance fatigue testing apparatus of FIG. 7.
Wherein, 1, a vibration table; 2. mounting a bottom plate; 3. a sample support frame; 4. a sample piece; 5. pre-tightening the bolts; 6. a mass block; 7. mounting holes; 8. a limiting rod; 9. a limiting hole; 10. a buffer ring; 11. a locking retainer ring for the shaft; 12. a first locknut; 13. a second locknut; 14. a vibration control instrument; 15. a power amplifier.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a method for testing the vibration fatigue performance of a metal in an axial resonance state, which can be seen in figure 5 and comprises the following steps:
s1: the method comprises the following steps of designing the form and size of an axial sample piece by combining the vibration environment of a material and the physical performance parameters of the material, specifically, after the sample is processed, checking the shape and size of a notch by using an optical instrument, wherein the actual size of the sample is required to be within the tolerance range of a drawing, the surface roughness needs to meet the drawing requirement, and no detectable crack or obvious defect exists.
And acquiring the buckling value and the modal parameter of the test piece through finite element software to determine whether the test piece can be used for the test of the vibration fatigue performance in the axial resonance state. After selecting a proper sample piece, adhering at least 2 strain gauges to a test section of a selected part of the sample piece, ensuring that the direction of the strain gauges is consistent with the axial direction of the sample piece and the strain gauges are symmetrically distributed, and measuring the response acceleration-strain/stress relation of the sample piece in a resonance state;
s2: calculating the response acceleration of the test piece during formal test according to the response acceleration-strain/stress relation and by combining the planned stress level;
s3: carrying out modal testing on the test piece to obtain a natural frequency point and a response amplitude ratio of axial vibration of the test piece;
s4: setting excitation frequency according to the natural frequency point measured by the test piece, and calculating excitation acceleration according to the response amplitude ratio measured by the test piece;
s5: during testing, the real-time excitation acceleration value of the test piece is combined for fine adjustment, so that the target response acceleration change of the test piece in the testing process is within +/-2%;
s6: setting a resonance search and a resonance residence program to enable the test piece to keep a resonance state in the test process, and stopping the test when the response acceleration of the test piece suddenly drops, such as 3dB, or the test piece is broken; and acquiring the cycle number of the vibration system when the test is stopped. And fitting an SN curve or a gN curve after the cycle times of the vibration system when the test is stopped are obtained.
Specifically, in the step (1), at least 3 different excitation accelerations are input to a natural frequency point of a test piece, different response levels of the excitation accelerations comprise high and low cycle fatigue performance of a material, strain data of multiple cycle periods are collected after each excitation acceleration is stable in the test piece, and then a response acceleration-strain relation is fitted;
according to the response acceleration-strain relation, calculating the response acceleration-stress relation according to the formula (I):
sigma ═ E epsilon (one)
In the formula: σ is the stress, E is the elastic modulus of the material, and ε is the measured strain of the test piece.
Strain data of 1000-10000 cycle periods are collected after the test piece is stabilized by each excitation acceleration.
And acquiring a response acceleration value of the test piece during the test according to the response acceleration-stress relation and the planned stress level, and then executing the first step and the second step to acquire an axial natural frequency point and a response amplitude ratio of the test piece to obtain an excitation acceleration and a frequency value during the formal test.
And (3) setting a resonance searching and resonance resident program according to the measured excitation acceleration and frequency values of the test piece:
a. the natural frequency point of the test piece is +/-10 Hz;
b. calculating the excitation acceleration according to the corresponding stress level and amplitude ratio, and constantly controlling the excitation acceleration value;
c. a-90 phase tracking is used.
Specifically, in the step (3), the method for acquiring the natural frequency point and the response amplitude ratio of the axial vibration of the sample includes:
firstly, carrying out resonance exploration on a test piece to obtain a resonance frequency point of the test piece and a response acceleration value of the point;
secondly, calculating an extreme value of the difference value of the response accelerations of the acceleration sensor on the mass block of the ith time (i is more than or equal to 1 and less than or equal to n), wherein the ratio of the extreme value of the difference value to the average value of the multiple response accelerations is xiSquaring the mean ratio of the single calculation to obtain xi 2Then the square value of the ratio of the average value of n times (n is more than or equal to 3) of resonance exploration is summed and the root is extracted, namely
If the obtained value is within 1 percent, namely Y is less than or equal to 1 percent, the response coaxiality of the test piece is good, otherwise, the response coaxiality of the test piece is not good.
The method for carrying out resonance exploration on the test piece is sine frequency sweep exploration, wherein pre-exploration is carried out firstly, and then formal exploration is carried out, and the control elements comprise: controlling acceleration, frequency sweep range, frequency sweep rate and frequency sweep cycle number; the control acceleration of the pre-probing is 0.1-2g, the sweep frequency range is 5-2000Hz, the sweep frequency rate is 0.5-2Oct/min, one sweep frequency cycle comprises a forward one time and a reverse one time, and the resonance frequency point of the forward sweep frequency and the reverse sweep frequency and the response acceleration value of the point are obtained; and adjusting and controlling the acceleration, the frequency range and the frequency sweeping rate according to the control parameters of the formal exploration according to the pre-exploration result.
The method for carrying out resonance exploration on the test piece is a random exploration method, wherein pre-exploration is carried out firstly, and then formal exploration is carried out, and the control elements comprise: controlling power spectral density value, frequency range, vibration duration; control power spectral density value of 0.001-0.05g for pre-probing2A white noise spectrum with the frequency range of 5-2000Hz and the vibration duration of the test piece after the response is stable is 30-120 seconds, and a resonance frequency point and a corresponding response acceleration value of the test piece are obtained; and adjusting the control power spectral density value and the frequency range according to the pre-probing result by the control parameters of the formal probing, and controlling the vibration duration of the test piece after the response is stable.
The following is a specific example of the operation performed in conjunction with the above method to more specifically illustrate the present invention.
In the invention, the test data processing method can adopt a grouping method and a lifting method for data processing.
Wherein the median logarithmic fatigue life in the method of grouping
Calculating according to the formula (1):
in the formula: n is a radical ofiThe fatigue life of the ith sample in each group of tests is shown; n is the number of each group of samples; n is a radical of50Fatigue life with 50% survival.
The standard deviation S of fatigue life is calculated as:
coefficient of variation CvComprises the following steps:
measurement of Material 10 by lifting method7The secondary fatigue strength, as shown in fig. 1, was plotted as a lifting graph during the test. The stress level in the lifting graph is about 4 grades, and at least 5 pairs of lifting pairs are arranged. The results are tabulated, as shown in table 1.
TABLE 1 lifting method results table (example)
Median fatigue limit
Comprises the following steps:
in the invention, the fatigue S-N curve is described by fitting the S-N curve by using a linear model and a nonlinear model, and the expressions of the two models are as follows:
linear model:
lgN＝A1+A2Smax (4)
lgN＝A1+A2lgSmax (5)
nonlinear model:
lgN＝A1+A2(Smax-S0) (6)
lgN＝A1+A2lg(Smax-S0) (7)
in the formula, A1，A2Is the S-N curve shape constant of the material under a certain stress concentration coefficient and stress ratio (or average stress); s0Is the fatigue limit of a material under a certain stress concentration coefficient and stress ratio (or average stress).
For the nonlinear model, let X be lgN and Y be Smax-S0(or Y ═ lg (S)max-S0) Equation (7) can be written as
X＝A1+A2Y (8)
And obtaining the S-N curve shape parameters and the correlation coefficient of the S-N curve shape parameters and the test data according to a least square method.
In the above formulae
LYY、LYXAre all equal to S0Is related to S0A function of (A)1、A2And r is also S0Is determined as a function of0The absolute value | r (S) of the correlation coefficient must be made0) | is the maximum value, so S can be obtained under the following conditions0：
Because of the fact that
So that there are
Order to
By substituting formulae (16) and (17) for formula (15), then
Is provided with
Is provided with
Is S0An estimated value of (2), then
When the temperature of the water is higher than the set temperature,
when in
When the temperature of the water is higher than the set temperature,
and due to S0Must be in the interval [0, S'0) In, S'0S as stress of data pointi(i is 1,2, …, n) minimum value, so that S can be easily obtained by bisection0. Finding a, b and S0Then, A can be obtained by the equations (9) and (10)1And A2. And processing the data according to the data processing method to obtain an S-N curve.
All data obtained by the test are drawn on a stress-life graph, the longitudinal axis of the stress adopts a linear coordinate, and the transverse axis of the fatigue life adopts a logarithmic coordinate; life 10 longer7The next point is added with a small arrow. One curve is plotted for each set of test results for each stress ratio. The S-N curves of different stress ratios under the same temperature condition are plotted on a graph, and the fatigue strength is compared. Figure 2 gives an example of a graphical report.
The test results obtained by the invention are as follows:
calibrating acceleration and strain relation: the relationship between the axial vibration response acceleration and the strain is shown in fig. 3, and it can be seen from the graph that the acceleration response value and the strain response value are in a positive correlation linear relationship.
The results of the axial vibration fatigue test data are shown in table 2, and as can be seen from table 2, the grouping method test data all meet the 95% confidence requirement, and the coefficient of variation value is smaller, which indicates that the data dispersibility is small and the test data is reliable.
TABLE 2 axial vibration fatigue test data
TABLE 3 results of S-N curve fitting formula for axial vibration fatigue test
According to the test results and the data processing method, an S-N curve of the axial vibration test is obtained and shown in FIG. 4, and an S-N curve fitting equation is shown in Table 3.
The method of the present invention is a general method, and can be applied to various test systems, for example, as an axial resonance fatigue test system adapted to the method of the present invention, see fig. 6, including an axial resonance fatigue test device, a vibration controller 14 and an acceleration sensor, wherein the vibration controller 14 is connected to the vibration table 1 and provides a vibration signal to the vibration table 1, and a power amplifier 15 is connected between the vibration controller 14 and the vibration table 1. The vibration table 1 generates vibration and transmits the vibration to a sample piece; at least one acceleration sensor is arranged on the vibration table 1, a plurality of acceleration sensors are arranged at the symmetrical positions of the mass block, and the acceleration sensors on the mass block are equal in mass and are uniformly and symmetrically distributed.
The axial resonance fatigue testing device can be seen from fig. 7 and 8, and comprises a vibration table 1, a mounting base plate 2, a sample supporting frame 3, a sample piece 4, a pre-tightening bolt 5 and a mass block 6, wherein the mounting base plate 2 is fixed on the vibration table 1, the sample supporting frame 3 is in an inverted U shape, the bottom of the sample supporting frame 3 is fixed on the mounting base plate 2, a mounting hole 7 is formed in the middle of the sample supporting frame 3, the pre-tightening bolt 5 is installed from the upper part of the mounting hole 7, the sample piece 4 is installed from the lower part of the mounting hole 7, the top of the sample piece 4 abuts against the bottom of the pre-tightening bolt 5, the bottom of the sample piece 4 is fixed on the mass block 6, the mass block 6 is located in the inverted U-shaped space of the sample supporting frame 3, and.
In order to prevent the sample from swinging during vibration, a limiting rod 8 is used for limiting the large swing of the sample piece 4, see fig. 7 and 8. Two limiting rods 8 penetrate through the mass block 6, the limiting rods 8 are symmetrically arranged on two sides of the sample piece 4, and the top and the bottom of each limiting rod 8 are respectively fixed on the sample supporting frame 3 and the mounting bottom plate 2. Two limiting holes 9 are formed in the mass block 6, and the limiting rod 8 penetrates through the limiting holes 9. Furthermore, the limiting rods 8 at the top and the bottom of the mass block 6 are respectively provided with a buffer ring 10 for buffering, and the outer side of the buffer ring 10 is provided with a locking retainer ring 11 for preventing collision. The upper part of the sample piece 4 is provided with a first locknut 12 for locking the sample support frame 3, and the lower part of the sample piece 4 is provided with a second locknut 13 for locking the mass block 6
Gaps are reserved between the limiting rod 8 and the limiting hole 9, the limiting rod 8 has three functions, firstly, if vibration is too severe or the coaxiality of the sample piece 4 is not good, problems are easy to occur, the limiting rod 8 is not in contact with the sample piece 4, and the sample piece can be well prevented from swinging greatly; secondly, after the sample piece 4 is broken, the mass block 6 is easy to fly out, and the mass block 6 is limited by the limiting rod 8; thirdly, the vibration table 1 can be protected. Preferably, the diameter of the stop rod 8 is at least 1mm smaller than the diameter of the stop hole 9.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (8)
1. The utility model provides a vibration fatigue performance test method under metal axial resonance state, is applicable to axial resonance fatigue testing arrangement, includes shaking table, mounting plate, sample braced frame, sample spare and quality piece, and mounting plate fixes on the shaking table, and the bottom of sample braced frame is fixed on mounting plate, and the sample spare is located sample braced frame, and the bottom of sample spare is fixed on the quality piece, and the quality piece is located the mounting plate top, its characterized in that, the vibration fatigue performance test method includes the following step:
(1) selecting a test piece, attaching a strain gauge, and measuring the response acceleration-strain/stress relation of the test piece in a resonance state;
(2) calculating the response acceleration of the test piece during formal test according to the response acceleration-strain/stress relation and by combining the planned stress level;
(3) carrying out modal testing on the test piece to obtain a natural frequency point and a response amplitude ratio of axial vibration of the test piece;
the method for acquiring the natural frequency point and the response amplitude ratio of the axial vibration of the sample comprises the following steps:
firstly, carrying out resonance exploration on the test piece to obtain a resonance frequency point of the test piece and a response acceleration value of the point;
secondly, calculating an extreme value of the difference value of the response accelerations of the acceleration sensor on the mass block for the ith time (i is more than or equal to 1 and less than or equal to n), wherein the ratio of the extreme value of the difference value to the average value of the multiple response accelerations is xiSquaring the mean ratio of the single calculation to obtain xi 2Then the square value of the ratio of the average value of n times (n is more than or equal to 3) of resonance exploration is summed and the root is extracted, namely
If the obtained value is within 1 percent, namely Y is less than or equal to 1 percent, the response coaxiality of the test piece is good, otherwise, the response coaxiality of the test piece is not good;
acquiring a response acceleration value of a test piece during a test according to a response acceleration-stress relation and a planned stress level, then executing a first step and a second step, acquiring an axial natural frequency point and a response amplitude ratio of a test sample, and acquiring an excitation acceleration and a frequency value during a formal test;
(4) setting excitation frequency according to the natural frequency point measured by the test piece, and calculating excitation acceleration according to the response amplitude ratio measured by the test piece;
(5) during testing, the real-time excitation acceleration value of the test piece is combined for fine adjustment, so that the target response acceleration change of the test piece in the testing process is within +/-2%;
(6) setting a resonance search and a resonance residence program to enable the test piece to keep a resonance state in the test process, and stopping the test when the response acceleration of the test piece suddenly drops or the test piece is broken; and acquiring the cycle number of the vibration system when the test is stopped.
2. The vibration fatigue performance testing method according to claim 1, wherein in the step (1), the method of selecting the test piece is: and acquiring the buckling value and the modal parameter of the test piece to determine whether the test piece can be used for the axial resonance state vibration fatigue performance test.
3. The vibration fatigue performance test method according to claim 1, characterized in that: the method for carrying out resonance exploration on the test piece is sine frequency sweep exploration, wherein the sine frequency sweep exploration is carried out firstly, then the pre-exploration is carried out, and then the formal exploration is carried out, and the control elements comprise: controlling acceleration, frequency sweep range, frequency sweep rate and frequency sweep cycle number; the control acceleration of the pre-probing is 0.1-2g, the sweep frequency range is 5-2000Hz, the sweep frequency rate is 0.5-2Oct/min, one sweep frequency cycle comprises a forward one time and a reverse one time, and the resonance frequency point of the forward sweep frequency and the reverse sweep frequency and the response acceleration value of the point are obtained; and adjusting and controlling the acceleration, the frequency range and the frequency sweeping rate according to the control parameters of the formal exploration according to the pre-exploration result.
4. The vibration fatigue performance test method according to claim 1, characterized in that: the method for carrying out resonance exploration on the test piece is a random exploration method, pre-exploration is carried out firstly,and then performing formal exploration, wherein the control elements comprise: controlling power spectral density value, frequency range, vibration duration; control power spectral density value of 0.001-0.05g for pre-probing2A white noise spectrum with the frequency range of 5-2000Hz and the vibration duration of the test piece after the response is stable is 30-120 seconds, and a resonance frequency point and a corresponding response acceleration value of the test piece are obtained; and adjusting the control power spectral density value and the frequency range according to the pre-probing result by the control parameters of the formal probing, and controlling the vibration duration of the test piece after the response is stable.
5. The vibration fatigue performance testing method according to claim 2, wherein in the step (1), not less than 3 different excitation accelerations are input to a natural frequency point of the test piece, different response levels of the excitation accelerations include high and low cycle fatigue performance of the material, and each excitation acceleration acquires strain data of a plurality of cycle periods after the test piece is stabilized, and then the response acceleration-strain relationship is fitted;
according to the response acceleration-strain relation, calculating the response acceleration-stress relation according to the formula (I):
sigma ═ E epsilon (one)
In the formula: σ is the stress, E is the elastic modulus of the material, and ε is the measured strain of the test piece.
6. The vibration fatigue performance testing method according to claim 5, wherein strain data of 1000-10000 cycles of cycle period are collected after the test piece is stabilized for each excitation acceleration.
7. The vibration fatigue performance testing method according to claim 1, wherein a resonance search and resonance dwell program is set according to the measured values of the excitation acceleration and frequency of the test piece:
a. the natural frequency point of the test piece is +/-10 Hz;
b. calculating the excitation acceleration according to the corresponding stress level and amplitude ratio, and constantly controlling the excitation acceleration value;
c. a-90 phase tracking is used.
8. The vibration fatigue performance test method according to claim 1, wherein after the number of cycles of the vibration system at the time of test stop is obtained, an SN curve or a gN curve is fitted.
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| CN110927249B (en) * | 2019-11-28 | 2022-09-27 | 北京机电工程研究所 | Lightweight high-strength composite material stress resonance fatigue test method and test system |
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